La mise en évidence des nanotubes de carbone mono-feuillets (SWCNTs) en 1993 par S. Iijima a été une des découvertes qui a marqué la recherche dans le domaine des nanos. L'étude de leurs propriétés a révélé qu'elles étaient supérieures à celles de matériaux déjà connus et a laissé entrevoir un champ très large d'applications potentielles. Les méthodes de synthèse actuelles permettent de produire des SWCNTs en grande quantité. Cependant, les échantillons de SWCNTs peuvent être hétérogènes tant au niveau de leur composition (impuretés carbonées et métaux catalytiques) qu'en ce qui concerne les caractéristiques des SWCNTs eux-mêmes. Des traitements post-synthèses sont donc indispensables pour améliorer les caractéristiques des échantillons. Dans ce travail, nous avons dans un premier temps mis en oeuvre une procédure de purification (multi-étape) couramment utilisée. En accord avec la littérature, l'optimisation des paramètres expérimentaux notamment en ce qui concerne le traitement d'oxydation n'a pas permis d'obtenir de bons rendements de purification et une sélectivité de réaction performante. Une méthode de purification alternative a été développée. Elle consiste essentiellement à un traitement thermique sous flux de dichlore. Elle a permis de diminuer significativement la proportion d'impuretés métalliques tout en préservant les nanotubes. Elle s'est également révélée efficace avec des échantillons produits selon différentes méthodes. L'autre difficulté majeure dans l'utilisation des nanotubes est leur processabilité. La modification de l'état de surface des nanotubes passe par la fonctionnalisation chimique. Pour cela, nous avons étudié le greffage de fonctions sondes / The discovery of single-walled carbon nanotubes (SWCNTs) in 1993 by S. Iijima has been one of the milestones of scientific research in the domain of nanos. The study of their properties has revealed that they were superior to those of materials already known and has let to foresee a field of numerous potential applications. The actual methods of synthesis enable to produce SWCNTs in large quantities. However, the SWCNT samples can be heterogeneous regarding both their composition (carbonaceous and metal impurities) and the features of the as-produced SWCNTs. Post-synthesis treatments are therefore indispensable to improve the characteristics of the samples. In this work, firstly we have carried out a standard multi-step purification procedure. In agreement with literature, the optimization of experimental parameters notably those used for the oxidation treatment did not permit us to obtain neither good yields of purification nor efficient selectivity of reaction. An alternative purification method has thus been developed. It consists mainly in a thermal treatment under a dichlore stream. It has enabled to significantly decrease the proportion of metallic impurities in the samples while preserving the nanotubes. It has also shown that this new purification process was efficient with samples produced by different methods. The other main difficulty in using nanotubes is their processability. Chemical functionalization is then needed to modify nanotube surface properties. In that case, we have studied the grafting of probe functions

Cette thèse comporte trois parties principales : la première concerne la synthèse et la fonctionnalisation des nanoparticules (NPs) d’or de forme sphérique et cylindrique. Les NPs d’or sont obtenues par réduction d’un sel métallique. En faisant varier certains paramètres de synthèse tels que la concentration en sels et/ou la concentration en réducteur, on peut facilement ajuster la taille de NPs sphériques. Bien qu’il existe diverses méthodes permettant de préparer des NPs cylindriques, il subsiste un problème de reproductibilité basée sur la pureté des produits de synthèse. Les différentes analyses de CTAB nous ont permis de proposer des solutions à ce problème. La fonctionnalisation de la surface des NPs d’or permet d’apporter à ces dernières de nouvelles propriétés tout en conservant leurs propriétés intrinsèques. Le but de cette fonctionnalisation est de modifier la surface des NPs en fonction des applications visées. Nous présentons ainsi différentes études de fonctionnalisation par des polyélectrolytes (PEI et PSS), des couches oxydes de SiO2, et de TiO2 et par le TDBC. La réponse optique des NPs d’or étant sensible à l’indice de réfraction du milieu environnant, il est possible de suivre et de quantifier cette fonctionnalisation par spectroscopie d’absorption. Dans une seconde partie, nous avons développé une voie de synthèse simple permettant de préparer le cœur coquille Au@TDBC sans ajout supplémentaire de sels ou de bases et à température ambiante. Etant donné qu’il est possible de moduler la taille des particules, l’optimisation du couplage fort entre les transitions électroniques du TDBC et les modes plasmon de résonances des Nps d’Au a été obtenu correspondant à une énergie de Rabi de 220 meV valeur qui n’a pas encore été obtenue avec un tel système. Dans une troisième partie, nous avons développé une nouvelle approche basée sur la méthode de Stöber pour fonctionnaliser les NPs avec des couches d’oxyde de SiO2 et de TiO2. L’utilisation des systèmes Au@TiO2 est une perspective intéressante en photocatalyse car le contact entre le métal et le semi-conducteur devrait entrainer une nette augmentation de l’efficacité photocatalytique. En effet, le métal agit comme un réservoir de photoélectrons améliorant le transfert de charges interfaciales tout en retardant la recombinaison des paires électrons-trous photo excités du semi-conducteur. / This thesis has three main parts: the first part relates to the synthesis and the functionalization of spherical gold nanoparticles (NPs) and nanorods. Gold NPs are obtained by chemical reduction of gold salt. By varying some synthesis parameters such as gold salt concentration and or reducing agent concentration, we can easily adjust the size of gold NPs. Different methods can be used to prepare gold nanorods, but there is a problem of reproducibility. This problem is based on the purity of products used to prepare gold nanorods. Different analysis of CTAB allowed us to propose solutions to this problem. Functionalization brings to gold NPs new properties. The aim of the functionalization is to modify the surface of gold NPs based on the intended applications. We present various functionalization of Au NPs by polyelectrolytes (PEI and PSS), oxides (SiO2 and TiO2) and TDBC. The optical response of Au NPs is sensitive to the refractive indexe of the surrounding medium, it is then possible to monitor and quantify this functionalization by absorption spectroscopy. In the second part of this work, we have developed a simple synthetic route for preparing Au@TDBC core shell without additional salts or bases at room temperature. Since it is possible to vary the particle size, optimization of the strong coupling between the electronic transitions of TDBC and the resonance plasmon of Au Nps obtained correspond to Rabi energy of 220 meV value which has not yet been achieved with such a system. In the third part, we have developed a new approach based on the Stöber method to functionalize the NPs with an oxide layer of SiO2 and TiO2. The use of Au@TiO2 core shell system is an interesting perspective in photocatalysis because the contact between metal and semiconductor should cause a marked increase in the photocatalytic efficiency. Indeed, the metal acts as a reservoir of photoelectrons improving the interfacial charge transfer while retarding the recombination of electron-hole pair of the semiconductor.

L'objectif de ce travail de recherche est la réalisation de dispositifs à base de nanofils de silicium, réalisés par la méthode des espaceurs. La synthèse des nanofils est effectuée à partir d'une couche de silicium polycristallin, déposée par la technique LPCVD (Low Pressure Chemical Vapor Deposition). Ces nanofils sont ensuite intégrés dans les dispositifs électroniques tels que des résistances ou des transistors réalisés suivant deux configurations différentes « bottom-gate » et « step-gate ». Les caractéristiques électriques de ces deux types de transistors ont mis en évidence des propriétés électriques suffisantes pour leur utilisation en tant que capteurs. Une simulation permet d'expliquer l'effet de l'apport de charges électriques à la surface des nanofils sur la concentration d'électrons dans la couche active. Les dispositifs sont tout d'abord utilisés pour la mesure du pH, et montrent une sensibilité de détection supérieure à la sensibilité nernstienne. Pour une utilisation du dispositif en tant que biocapteur, une fonctionnalisation de la surface des nanofils est nécessaire pour permettre l'accrochage de sondes d'ADN. La détection électronique de l'hybridation sondes/cibles de brins d'ADN complémentaires est démontrée avec un faible seuil de détection. Enfin, afin d'augmenter la surface d'échange entre le nanofil et les espèces chargées, un procédé de fabrication de résistances à base de nanofils suspendus est développé. Des tests de détection en présence d'ammoniac ont mis en évidence une réponse linéaire sur une gamme de concentrations. Les résistances à base de nanofils suspendus présentent une plus grande sensibilité que celles à base de nanofils non suspendus, mettant en avant l'effet important de la surface des nanofils. Tous ces résultats permettent de démontrer la faisabilité de capteurs chimiques et biologiques à base de nanofils de silicium à partir des techniques conventionnelles de la microélectronique en utilisant un procédé de fabrication « bas-coût ». / The goal of this research work is the realization of devices based on silicon nanowires, realized using sidewall spacer formation technique. Nanowires are synthesized form a polycrystalline silicon layer deposited by LPCVD technique (Low Pressure Chemical Vapor Deposition). These nanowires are then integrated into electronic devices such as resistors and transistors made using two different configurations “bottom-gate” and “step-gate”. The electrical characteristics of these two types of transistors have shown adequate electrical properties for their use as sensors. A simulation is made, to explain how additional electrical charges on the surface of the nanowires, affect the electron concentration inside the active layer. The devices are firstly used for the pH measurement, and have shown sensitivity higher than the Nernstian sensitivity detection. For a use as biosensor, nanowires are functionnalized to allow the binding of DNA probes. Electronic detection of hybridization complementary probe/target DNA strands is demonstrated with a low detection limit. Finally, in order to increase the exchange surface between the nanowires and charged species, resistors based on suspended nanowires were developed. Different tests were performed in the presence of ammonia and showed a linear response over a range of concentrations. Resistors based on suspended nanowires highlighted greater sensitivity than those based on unsuspended nanowires, bringing out the important effect of the surface of the nanowires. All these results demonstrate the feasibility of chemical and biological sensors based on silicon nanowires compatible with conventional microelectronics techniques using a low-cost process.

Les nanodiamants font l'objet d'un intérêt croissant dans différents domaines tels que la physique (grâce aux propriétés photo-physiques dues aux défauts azotés dans la maille cristalline), la chimie des matériaux (synthèse de nouveaux matériaux composites avec des performances mécaniques accrues), la tribologie (lubrification, polissage) et la biologie (comme agents de contraste ou vecteurs de molécules actives, …). Le développement de nouveaux matériaux fonctionnels à base de nanodiamants nécessite de poursuivre des études fondamentales sur la fonctionnalisation et la caractérisation de leur surface. Plusieurs méthodes de fonctionnalisation de surface ont déjà été proposées, mais beaucoup de possibilités n'ont pas encore été explorées.L'objectif de ce projet de recherche est de mettre au point de nouvelles voies de modification de surface de nanodiamants et de développer des techniques de caractérisation de ces matériaux. Les nanodiamants que nous étudions sont commerciaux. Ils sont obtenus par détonation puis purifiés et comportent des fonctions oxygénées en surface (alcool, acide carboxylique, cétone, etc). Nous proposons de fonctionnaliser la surface de ces nanodiamants en faisant réagir les fonctions alcool de surface avec des chlorures d'acides phosphorique ou phosphonique. Une première partie des résultats concerne le greffage par le trichlorure de phosphoryle (POCl3) conduisant à la fonctionnalisation par des espèces phosphates. La seconde partie présente le greffage de chlorure d'acides phosphoniques (RPOCl2) permettant le greffage de phosphonates.Les nanodiamants modifiés sont étudiés par différentes techniques de caractérisation, notamment par spectroscopie infrarouge (FTIR), analyse thermogravimétrique (ATG), résonance magnétique nucléaire (RMN) en phase solide du 31P, 13C et 1H, analyses élémentaires, diffraction des rayons X (DRX) et microscopie électronique à transmission (MET).Enfin, en collaboration avec l'Ecole des Mines d'Alès, nous avons débuté l'étude de composites polymère/nanodiamants, et les premiers résultats sont présentés dans une troisième partie. / Nanodiamonds are increasingly studied in different fields such as physics (through spontaneous photoluminescence properties due to nitrogen-vacancy centers), tribology (lubrication, polishing), materials science (nanocomposites) or biology (drug or gene delivery, bio-labeling). The development of nanodiamonds-based materials with new properties requires continuing further fundamentals studies on the functionalization and characterization of their surface. Several methods of surface functionalization have already been proposed but many possibilities have not yet been explored.The objective of this research project is to develop new ways of surface modification of nanodiamonds and develop techniques for the characterization of these materials. The nanodiamonds studied here are commercial. They are obtained by detonation then purified and their surface is covered by oxygenated functions (alcohol, carboxylic acid, ketone, aldehyde, etc.). We propose to functionalize the surface of these nanodiamonds by reacting the alcohol surface functions with phosphoric or phosphonic acid chlorides. The first part of the results concerns the grafting by phosphoryl trichloride (POCl3) leading to the functionalization by phosphate species. The second part presents the grafting of phosphonic acid chlorides (RPOCl2) leading to phosphonate surface species.Surface modifications are monitored by several characterization methods such as infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), nuclear magnetic resonance spectroscopy (1H, 13C and 31P solid-state NMR), elemental analysis, X-ray diffraction (XRD) and transmission electronic microscopy (TEM).In addition, in collaboration with the Ecole des Mines d'Alès, we started the study of polymer/nanodiamonds composites, and the first results are presented in a third part.

Reductive functionalization of methyl ligands by 3d metal catalysts and two possible side reactions has been studied. Selective oxidation of methane, which is the primary component of natural gas, to methanol (a more easily transportable liquid) using organometallic catalysis, has become more important due to the abundance of domestic natural gas. In this regard, reductive functionalization (RF) of methyl ligands in [M(diimine)2(CH3)(Cl)] (M: VII (d3) through CuII (d9)) complexes, has been studied computationally using density functional techniques. A SN2 mechanism for the nucleophilic attack of hydroxide on the metal-methyl bond, resulting in the formation of methanol, was studied. Similar highly exergonic pathways with very low energy SN2 barriers were observed for the proposed RF mechanism for all complexes studied. To modulate RF pathways closer to thermoneutral for catalytic purposes, a future challenge, paradoxically, requires finding a way to strengthen the metal-methyl bond. Furthermore, DFT calculations suggest that for 3d metals, ligand properties will be of greater importance than metal identity in isolating suitable catalysts for alkane hydroxylation in which reductive functionalization is used to form the C—O bond. Two possible competitive reactions for RF of metal-methyl complexes were studied to understand the factors that lower the selectivity of C—O bond forming reactions. One of them was deprotonation of the methyl group, which leads to formation of a methylene complex and water. The other side reaction was metal-methyl bond dissociation, which was assessed by calculating the bond dissociation free energies of M3d—CH3 bonds. Deprotonation was found to be competitive kinetically for most of the 1st row transition metal-methyl complexes (except for CrII, MnII and CuII), but less favorable thermodynamically as compared to reductive functionalization for all of the studied 1st row transition metal complexes. Metal-carbon bond dissociation was found to be less favorable than the RF reactions for most 3d transition metal complexes studied. The first dinitrogen dicopper (I) complex has been characterized using computational and experimental methods. Low temperature reaction of the tris(pyrazolyl)borate copper(II) hydroxide {iPr2TpCu}2(µ-OH)2 with triphenylsilane under a dinitrogen atmosphere gives the µ -N2 complex, {iPr2TpCu}2(µ -N2). X-ray crystallography reveals an only slightly activated N2 ligand (N-N: 1.111(6) Å) that bridges between two iPr2TpCuI fragments. While DFT studies of mono- and dinuclear copper dinitrogen complexes suggest a weak µ-backbonding between the d10 CuI centers and the N2 ligand, they reveal a degree of cooperativity in the dinuclear Cu-N2-Cu interaction.

Este trabalho teve como objetivo a modificação de óleo de soja por meio da sua funcionalização com grupos hidroxílicos visando seu uso na síntese de poliuretanos. As reações de funcionalização foram conduzidas em duas etapas, uma de epoxidação seguida de hidroxilação utilizando álcoois de baixo peso molecular como agente hidroxilante. Na primeira etapa do processo, a epoxidação, duas amostras foram obtidas variando o grau de funcionalidade de aproximadamente 2 mol de epóxido por mol de óleo epoxidado (F2) e, aproximadamente, 2,5 mol de epóxido por mol de óleo epoxidado (F2,5). Na segunda etapa, variou-se os álcoois utilizados como agentes hidroxilantes da amostra F2 entre metanol, etanol, isopropanol e 1-butanol; enquanto que a amostra F2,5 foi hidroxilada apenas com etanol. Os óleos modificados foram caracterizados por meio de espectroscopia na região do infravermelho (FTIR), espectroscopia de ressonância magnética nuclear de prótons (RMN 1H); determinação do percentual de epóxido, índice de hidroxila e de acidez, distribuição de massa molar e viscosidade dinâmica. Os resultados obtidos foram comparados com os valores típicos do óleo de mamona que por ser naturalmente hidroxilado é muito usado na síntese de poliuretanos. A caracterização estrutural permitiu comprovar a eficácia da síntese, apresentando evidências claras quanto às diferenças estruturais existentes entre as amostras funcionalizadas e o óleo de mamona. As técnicas de FTIR e RMN 1H mostraram a formação do grupo beta-hidroxi-éter, vicinal à hidroxila, de acordo com o tipo de álcool usado na hidroxilação de cada uma das amostras. Variações entre a estimativa do índice de hidroxila, através do percentual de epóxido e o índice de hidroxila experimental sugeriram reações paralelas durante a síntese. A influência da acidez durante o processo e a acidez final de cada uma das amostras também foi determinada. As curvas de GPC comprovaram umas das vias paralelas sugeridas com a formação de fases oligoméricas entre os triglicerídeos. A viscosidade final apresentou grande variação, principalmente em função do grupo beta-hidroxi-éter formado em cada caso, do grau de funcionalidade, além da redução do teor de insaturações do óleo modificado. Dados sobre a energia de ativação de escoamento do fluido em função da temperatura mostraram que o fator mais significativo na variação da viscosidade é o índice de hidroxila final das amostras. As amostras sintetizadas foram usadas na polimerização de poliuretanos. A reatividade das amostras foi determinada através de ensaios de cura acompanhados por FTIR, além de uma caracterização mecânica dos poliuretanos finais feita por Análise Dinâmico Mecânica (DMA). As amostras apresentaram uma alta variação quanto à reatividade no processo de polimerização. Os ensaios de DMA mostraram a relação direta entre a temperatura de transição vítrea e o grau de funcionalidade, além do efeito plastificante gerado pelas cadeias livres contidas na fase flexível formada pelos triglicerídeos parcialmente funcionalizados. / The objective of this work was the modification of soybean oil by its functionalization with hydroxyl groups for its use in the synthesis of polyurethanes. Functionalization reactions were conducted in two steps, one epoxidation followed by hydroxylation using low molecular weight alcohols as hydroxylating agent. In the first step, two samples were obtained varying the degree of functionality of approximately 2 moles of epoxide per mole of epoxidized oil (F2) and approximately 2.5 moles of epoxide per mole of epoxidized oil (F2,5). In the second step, the process was varied using different alcohols as hydroxylating agents of the F2 sample, which were methanol, ethanol, isopropanol and 1-butanol; while the F2.5 sample was hydroxylated only with ethanol. The modified oils were characterized by Infrared Spectroscopy (FTIR), Proton Nuclear Magnetic Resonance Spectroscopy (1HNMR), determination of the percentage of epoxide, hydroxyl and acidity index, molar mass distribution and dynamic viscosity (Brookfield viscosity). The obtained results were compared to the typical values of castor oil which, because it is naturally hydroxylated, is widely used in the synthesis of polyurethanes. The structural characterization allowed proving the efficacy of the synthesis, presenting clear evidence regarding the structural differences between the functionalized samples and castor oil. The results from FTIR and 1HNMR techniques showed the formation of the beta-hydroxyl ether group, side to the hydroxyl, according to the type of alcohol used in the hydroxylation of each of the samples. Variations between the estimation of the hydroxyl number, through the percentage of epoxide and the experimental hydroxyl number, suggested parallel reactions during the synthesis. The influence of the acidity during the process and the final acidity of each of the samples were also determined. The GPC curves confirmed one of the parallel pathways suggested with the formation of oligomeric phases between the triglycerides. The final viscosity showed great variation according to the beta-hydroxyl ether group formed in each case, the degree of functionality and the reduction of unsaturation content in the modified oil. Activation energy values of fluid flow as a function of temperature showed that the most significant factor in the viscosity variation is the final hydroxyl number of samples. The synthesized samples were used in the polymerization of polyurethanes. The reactivity of the samples was determined by curing tests monitored by FTIR technique, in addition to a mechanical characterization of final polyurethanes by Dynamic Mechanical Analysis (DMA). The samples showed a high variation in reactivity in the polymerization process. The DMTA tests showed the relationship between the glass transition temperature and the degree of functionality in addition to the plasticizing effect generated by free chains contained in the flexible phase formed by the partially functionalized triglycerides.

Le bois est un matériau à la fois naturel, renouvelable, recyclable et biodégradable. Cependant, malgré ses qualités, il présente, comme tout autre matériau, quelques inconvénients. Ce sujet de thèse porte sur une étude de faisabilité technologique d’enrichissement d’un substrat bois par des charges, aux propriétés physiques et chimiques données, incorporées par voie physique au moyen d’un procédé innovant qui est le procédé de jet d’azote à haute pression installé dans la plateforme expérimentale du CRITT-TJFU. L’innovation consiste à conférer aux particules des vitesses élevées (400-700 m/s) par la seule action de la pression hydrodynamique du flux d’azote, sans apport de chaleur. Les températures mises en jeu sont compatibles pour un usage sur bois sans altération des propriétés mécaniques et géométriques de la structure enrichie. Trois essences de bois (sapin, peuplier et hêtre) ont été traitées sous différentes conditions d’impact de deux types de particules (grenat et cuivre). Les caractérisations réalisées que ce soit par techniques d’imageries ou encore les caractérisations mécaniques, chimiques mais aussi microbiologiques ont montré que le bois traité par la technologie du jet d’azote acquière de nouvelles propriétés et s’enrichit par rapport à son état naturel / Wood is a material that is both natural, renewable, recyclable and biodegradable. However, despite its qualities, it presents, like any other material, some disadvantages. This PhD thesis deals with a technological feasibility study for the enrichment of a wood substrate by fillers, with specific physical and chemical properties, incorporated by physical means using an innovative process that is the nitrogen jet process at high pressure installed in the experimental platform of the CRITT-TJFU. The innovation consists in giving the particles high velocities (400-700 m/s) by the only action of the hydrodynamic pressure of the nitrogen flow, without any addition of heat. The temperatures are compatible for use on wood without altering the mechanical and geometrical properties of the enriched structure. Three types of wood (fir, poplar and beech) were treated under different impact conditions of two types of particles (garnet and copper). The characterizations carried out either by imaging techniques or even the mechanical, chemical but also microbiological characterizations have shown that wood treated by nitrogen jet technology acquires new properties and is enriched compared to its natural state

A funcionalização régiosseletiva e quimiosseletiva de arenos utilizando reagentes organometálicos têm sido uma ferramenta importante na síntese de novas moléculas de interesse científico e tecnológico, principalmente para a Química Medicinal. Neste contexto, o objetivo deste trabalho foi investigar a reatividade de amidetos metálicos na funcionalização de benzonitrilas, uma vez que o grupo ciano é um importante intermediário sintético e pode ser transformado em diversos grupos funcionais. Para tanto, inicialmente, cianofenóis foram convertidos aos respectivos pivalatos, carboxilatos e fosforodiamidetos, sendo estes grupos estudados como grupos orto-dirigentes de metalação. Com o objetivo de desenvolver metodologias para funcionalização dos substratos, diferentes amidetos de lítio e mistos de magnésio e lítio foram estudados sob diferentes condições reacionais, sendo iodo o eletrófilo padrão para monitoramento das reações. De maneira geral, observou-se pouca reatividade das bases mistas TMPMgCl?LiCl e TMP2MgCl?2LiCl frente aos substratos estudados. Por outro lado, a base TMPLi se mostrou efetiva na funcionalização dos substratos, sendo que os produtos de rearranjo de Fries foram sempre majoritários em detrimento aos produtos de iodólise. Com isso, diferentes benzonitrilas funcionalizadas de estrutura inédita na literatura puderam ser sintetizadas de maneira regiosseletiva, sendo os produtos caracterizados por meio de análises de RMN bidimensionais. Similarmente, na etapa final do projeto, a reatividade das mesmas bases foi investigada em reações com metóxi-benzonitrilas, sendo que neste caso os iodetos esperados foram obtidos em bons rendimentos pelo uso das bases mistas de magnésio e litio. Adicionalmente, os intermediários organometálicos demostraram boa reatividade frente a diversos eletrófilos, proporcionando o isolamento de benzonitrilas substituídas com diferentes grupos funcionais, sendo estas de grande interesse sintético e medicinal. / The regioselective and chemoselective functionalization of arenes using organometallic reagents has been an important tool for the synthesis of new molecules of scientific and technologic interest, especially for the Medicinal Chemistry. In this context, the objective of this work was to investigate the reactivity of metallic amides in the functionalization of benzonitriles once the cyano group is an important synthetic intermediate and can be transformed in several different functional groups. Thus, initially, cyanophenols were converted to the respective pivalates, carboxylates and phosphodiamides which were studied as ortho directing metalation groups. With the goal of developing methodologies for the functionalization of the cited substrates, different lithium amides and mixed lithium-magnesium amides were studied under different reaction conditions being iodide the standard electrophile for reaction monitoring. In general, it was observed little reactivity of the mixed bases TMPMgCl?LiCl and TMP2MgCl?2LiCl against the studied substrates. On the other hand, the TMPLi base has proved to be effective in the functionalization of the substrates though the Fries\' rearrangement products were always observed in majority compared to the iodolysis products. By using this strategy, several novel functionalized benzonitriles could be synthetized in a regioselective way with the products being characterized by bidimensional NMR techniques. Similarly, in the final stage of the project the reactivity of the same bases was investigated in reactions employing methoxi-benzonitriles where the mixed lithium-magnesium afforded the expected iodides in good yields. Additionally, the organometallic intermediates demonstrated good reactivity against several electrophiles providing the isolation of substituted benzonitriles of great synthetic and medicinal interest.

A importância que a catálise representa para a sociedade pode ser vista em números: 90% dos processos da indústria química e mais de 20% de todos os produtos industriais comercializados no mundo utilizam uma ou mais etapas catalíticas. Assim, desenvolver catalisadores eficientes, ativos e seletivos é a solução para criar tecnologias mais limpas e sustentáveis. Além disso, reações químicas que geram novas ligações C-C estão entre as transformações mais relevantes na química orgânica e são a base desse trabalho. Os catalisadores de ródio apresentados aqui fazem parte de um trabalho minucioso de desenvolvimento, síntese e caracterização de nanopartículas e suportes magnéticos funcionais que foram utilizados em transformações de diversas moléculas. O estudo inicial com nanopartículas de ródio suportadas, em reações de hidrogenação do cicloexeno, serviu para a compreensão de como se comportam essas nanoestruturas e da influência que diferentes ligantes orgânicos e estabilizantes podem ter em uma aplicação catalítica bastante conhecida. O sistema catalítico mostrou-se bastante ativo e reutilizável,despertando o nosso interesse ao seu aperfeiçoamento para aplicação em reações de hidroformilação. Antes da síntese de catalisadores suportados, estudos com nanopartículasnão-suportadas mostraram que um sistema modificado pela adição de fosfinas era necessário para ativação do catalisador e que o estabilizante utilizado afetava a atividade catalítica. Assim, para possibilitar o ancoramento eficiente das espécies ativas, uma modificação da superfície do suporte magnético com a metildifenilfosfina foi realizada. A fosfina funcionalizada sobre o suporte viabilizou sua interação com as espécies ativas e evitou a sua lixiviação, possibilitando o reuso do catalisador. A reação de hidroformilação do oct-1-eno atingiu 96% de conversão e 82% de seletividade para aldeídos, em 6 horas a 80°C. A carga metálica do catalisador foi de apenas 0,2%. Buscando aumentar a eficiência na etapa de imobilização do metal e uma melhor atividade catalítica que possibilitasse o uso de substratos mais complexos, o suporte magnético foi modificado com um polímero hiper-ramificado. Essa modificação possibilitou aumentar a quantidade de grupos fosfinas sobre o suporte, assim como levou a um significativo aumento na carga de metal. A reação de hidroformilação de produtos naturais foi possível e, com o composto estragol, conversões de 100% foram alcançadas em 6 horas, com seletividade de 70% para aldeídos. Mesmo com evidências que sugerem a formação de espécies ativas moleculares, o suporte modificado possibilitou que o catalisador mantivesse sua atividade e seletividade por pelo menos seis reações sucessivas. Os materiais desenvolvidos apresentaram estabilidade quando manuseados ao ar, sem prejudicar sua vida útil e fácil separação. / The importance of catalysis to society may be seen in numbers: 90% of chemical production processes and more than 20% of all industrial products sold in the world use one or more catalytic steps. Thus, the development of efficient, active, and selective catalysts is crucial for creating cleaner and sustainable technologies. In addition, chemical reactions that generate new C-C bonds are among the most important transformations in organic chemistry and are the basis of this work. Rhodium catalysts presented herein are part of a careful investigation, which included the development, synthesis and characterization of metal nanoparticles and magnetic functional supports for use in the transformation of various molecules. The initial study of supported rhodium nanoparticles in cyclohexene hydrogenation reactions has driven our understanding of the behavior of these nanostructures, and the influence that different ligands and stabilizers may have in a well-known catalytic application. The identification of a highly active and recyclable catalytic system aroused our interest for its improvement for application in hydroformylation reactions. Prior to the synthesis of supported catalysts, studies with non-supported nanoparticles revealed that a modified system with the addition of phosphines was required for activation of the catalyst and the stabilizer used affected the catalytic activity. Thus, to enable efficient immobilization of the active species, the surface of the magnetic support was modified with methyldiphenylphosphine. The catalyst preparation removed, at least partially, the stabilizer adsorbed on the nanoparticles surfaces. The phosphine-functionalized support anchored the active species and avoided their leaching, allowing the reuse of the catalyst. The hydroformylation reaction of oct-1-ene reached 96% of conversion and 82% of selectivity to aldehydes, in 6 hours at 80°C. The metal loading of the catalyst was only 0.2%. Seeking to increase the efficiency in metal immobilization step and a better catalytic activity that would enable the use of more complex substrates, the magnetic support was modified with a hyperbranched polymer, which allowed an increase in the amount of external phosphines, as well as a significant increase in metal loading on the support. The hydroformylation reaction of natural products was possible and, with the estragole compound, 100% of conversion was achieved in 6 hours with 70% of selectivity to aldehydes. Despite evidence that suggests the formation of active molecular species, the modified support has enabled the catalyst to retain its activity and selectivity for at least six successive reactions. The materials developed could be handled in air without damaging their catalytic activity, durability and separation properties.

Thesis advisor: Kian L. Tan / Chapter 1. Catalytic directing group, I, which was designed with the ability to form a reversible covalent bond with a substrate and bind a metal, was shown to direct the hydroformylation of allylic amines. The efficient regioselective hydroformylation of a variety of 1,2-disubstituted allylic sulfonamides to form β-amino-aldehydes under mild conditions has been shown. Chapter 2. Building off of the successful application of I, enantioenriched catalytic directing group, II, was designed and synthesized. It retained the essential features to direct hydroformylation to obtain good regioselectivity while also providing a chiral environment to induce absolute stereocontrol. Under mild conditions, a variety of disubstituted olefins react to give good yields and excellent enantioselectivites. Thus, the first enantioselective reaction performed with a catalytic directing group was demonstrated. Chapter 3. A new set of organocatalysts was developed that benefits from reversible covalent bonding and induced intramolecularity. The desymmetrization of meso-1,2-diols was accomplished using organocatalyst III, which was synthesized easily and cheaply. Experimental results indicate that the selectivity and increased reactivity are a result of the ability of III to pre-organize the substrate through a reversible, covalent bond. A variety of cyclic and acylic substrates were shown to react efficiently with good enantioselectivities under mild conditions. The catalyst's ability to functionalize cis-1,2-diols selectively indicated it might be successfully applied to site selective catalysis. Thus, the selective functionalization of a secondary alcohol in the presence of a primary alcohol was developed using a combination of binding selectivity and stereoselectivity. The (S)-enantiomer forms the secondary functionalized product while the (R)-enantiomer forms the primary functionalized product with high selectivity. As the enantiomers preferentially form different functionalized products, a regiodivergent reaction on a racemic mixture resulted giving two valuable enriched products. / Thesis (PhD) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.